1. Field
The present disclosure relates to devices for reducing a moisture carry over (MCO) level at the exit of a fuel bundle of a nuclear reactor.
2. Description of Related Art
Water enters a fuel bundle of a boiling water reactor (BWR) as a liquid and exits as steam, wherein the steam is used to drive a turbine. The water typically enters a fuel bundle through a tie plate. FIG. 1 is a perspective view of a conventional tie plate for a fuel bundle of a boiling water reactor. Referring to FIG. 1, a conventional tie plate 100 (e.g., lower tie plate) may include a rim 102 defining an entrance 104 with arc members 106 extending from the rim 102 and converging below a center of the entrance 104.
During the operation of a boiling water reactor, water is supplied to a fuel bundle through the entrance 104 of the tie plate 100. Ideally, the water exits the fuel bundle as pure steam. However, after a certain number of cycles, a fuel bundle will inevitably become a low power bundle and will be moved to one of the outer, peripheral rows along with the other low power bundles. Nevertheless, even if a low power bundle is arranged in one of the outer, peripheral rows, the steam exiting the low power bundle may still contain an increased amount of water droplets if the amount of incoming water exceeds the ability of the low power bundle to convert all of the water to steam.
The amount of water droplets in the steam exiting a fuel bundle may be referred to as a moisture carry over (MCO) level. A high moisture carry over level is detrimental to the operation of a boiling water reactor for at least two reasons. First, a high moisture carry over level increases the amount of radiation exposure to plant operators. Second, a high moisture carry over level causes damage to the blades of the steam turbine. Consequently, nuclear power plants typically opt to reduce core flow in order to decrease moisture carry over levels. However, a reduction in core flow results in a reduction in reactor power which ultimately results in decreased revenues.